The application of pressure and/or thermal energy is often used to treat various medical conditions.
For example, the combined application of pressure and temperature is taught in U.S. Pat. No. 5,074,285 for the treatment of sporting injuries such as bruising and muscle stiffness. In that system, thermal sources, which could be hot or cold, are introduced into pockets close to the wearer's skin and pressure is applied to a series of air pockets arranged along the limb that are designed to apply a pressure-gradient repeatedly to the limb.
Hypothermia is a condition resulting from a drop in body temperature and varies in degree according to the amount of undercooling. Many methods for treating hypothermia are already known. Generally, these comprise introducing heat into the core of the body by some means to raise the body temperature. Simple treatments can take the form of a warm drink. Sometimes warm air is blown around the body via air blankets.
One of the first physiological responses of hypothermia is peripheral vasoconstriction which reduces the amount of blood at the periphery of the body. This can make it difficult to introduce heat into the body through the application of heat to the body surface. It is known that vessels, including capillaries, arterioles, arteries, venules and veins, can be made to vasodilate under conditions of negative pressure. Vasodilated skin regions, particularly on the forearm, can make efficient heat transfer surfaces.
One system that applies negative pressure to a limb to reduce peripheral vasoconstriction whilst warming the periphery of the patient to treat hypothermia is taught in U.S. Pat. No. 5,683,438 and sold under the mark Thermostat® by Aquarius Medical Corp. In that system, a limb of the patient is placed in a sealed chamber and the pressure inside the chamber is reduced to a negative pressure of between −20 to −80 mmHg (−2.7 to −10.7 kPa). At the same time, thermal energy is delivered to the surface the limb using a thermal blanket, heat lamp or chemical heating elements. Further developments to this system are described in International Publication No. WO 01/80790 A1.
Recently, the application of a pulsating negative pressure has been found beneficial in the adjustment of a patient's core body temperature. Commonly owned U.S. Patent Application Publication No. 2005/0027218 describes a system for applying a pulsating pressure and adjusting the core body temperature of a patient which utilizes a liquid reservoir to effectuate heat and pressure transfer to a limb of the patient. Such application is herein incorporated in its entirety.